Fan control circuit

ABSTRACT

A fan control circuit of a computer includes a fan interface connected to a connector of a fan, a fan controller, a NOT gate, and an electronic switch. The fan controller outputs a PWM signal to the fan interface to control the operation of the fan, and includes a GPIO interface to output a voltage control signal to the NOT gate to switch the electronic switch on or off. A signal output of the electronic switch is connected to the fan interface. The voltage control signal is high level at the start up moment of the computer, and thus does not turn on the fan via the electronic switch. After a preset delay period, the voltage control signal is turned low by the fan controller so that the fan interface receives the PWM signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to a U.S. patent application entitled “FANCONTROL CIRCUIT,” with the same assignee as the instant application andwith the Attorney Docket No. US40027. The disclosure of the aboveidentified application is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a fan control circuit.

2. Description of Related Art

A server typically includes multiple fans, which rotate at full speed atthe moment of the server being started up. The power consumed by theinterior components of the server, such as motherboards, hard diskdrives and fans, can be up to a thousand kilowatts at the start upmoment, which may cause instability in the power supply to the server,and high power consumption. Delay circuitry has been used to make thefans start operating after a preset delay period, however, many delaycircuits include multiple extra components, which results in high cost.

BRIEF DESCRIPTION OF THE DRAWING

Many aspects of the embodiments can be better understood with referenceto the following drawing. The components in the drawing are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.

The drawing is a block diagram of an exemplary embodiment of a fancontrol circuit connected to a fan via a fan connector.

DETAILED DESCRIPTION

The disclosure, including the accompanying drawing, is illustrated byway of example and not by way of limitation. It should be noted thatreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

Referring to the FIGURE, an exemplary embodiment of a fan controlcircuit 100 of a computer includes a fan controller 90, an electronicswitch chip 40, a NOT gate 50, and a fan interface 30 for connectingwith a connector 25 of a fan 20.

The fan controller 90 includes a rotational speed control pin 16 whichoutputs a pulse width modulation (PWM) signal, and a general purposeinput/output (GPIO) interface 95 with a control pin 12 for outputting avoltage control signal. The rotational speed control pin 16 is connectedto a control pin 14 of the fan interface 30 to transmit the PWM signalto the fan interface 30 to control the operation of the fan 20. Thecontrol pin 12 of the GPIO interface 95 is connected to the input of theNOT gate 50 for outputting the voltage control signal, which is at ahigh level at the moment of the computer being started up, and after adelay period, becomes a low level signal under the control of the fancontroller 90.

The electronic switch chip 40 (e.g. NC7SV125P5X_DS chip) includes anenable terminal OE, a signal input A, and a signal output Y. The enableterminal OE and the signal input A of the electronic switch chip 40 areconnected to the output of the NOT gate 50, and the signal output Y iscoupled to the rotational speed control pin 16 of the fan controller 90.The electronic switch chip 40 is turned on when the enable terminal OEof the electronic switch chip 40 receives a low-level voltage controlsignal.

As the computer starts up, the control pin 12 of the GPIO interface 95outputs a high-level voltage control signal to the input of the NOT gate50. The NOT gate 50 inverts the signal which is then output to theenable pin OE and the signal input A of the electronic switch chip 40.The electronic switch chip 40 is turned on, and the low-level signalfrom the signal input A of the electronic switch 40 is transmitted tothe rotational speed control pin 16 of the fan controller 90 via thesignal output Y of the electronic switch chip 40. The governing signalat the rotational speed control pin 16 and the control pin 14 of the faninterface 30 is thereby low, which leaves the fan 20 turned off.

After a preset delay period, the voltage control signal at the controlpin 12 of the GPIO interface 95 becomes a low-level signal under thecontrol of the fan controller 90. The NOT gate 50 inverts again, and theresulting high-level signal is then sent to the enable terminal OE toturn off the electronic switch chip 40. The control pin 14 of the faninterface 30 receives a PWM signal from the rotational speed control pin16 of the fan controller 90 to start and control the operation of thefan 40.

The foregoing description of the exemplary embodiments of the disclosurehas been presented only for the purposes of illustration and descriptionand is not intended to be exhaustive or to limit the disclosure to theprecise forms disclosed. Many modifications and variations are possible.The embodiments are described in order to explain the principles of thedisclosure and their practical application so as to enable others ofordinary skill in the art to utilize the disclosure, with such variousmodifications as are suited to the particular use contemplated.Alternative embodiments will become apparent to those of ordinary skillsin the art to which the present disclosure pertains without departingfrom its spirit and scope. Accordingly, the scope of the presentdisclosure is defined by the appended claims rather than by theforegoing description and the exemplary embodiments described therein.

1. A fan control circuit of a computer, the fan control circuitcomprising: a fan interface connected to a connector of a fan of thecomputer, and comprising a first control pin; an electronic switchcomprising an enable terminal, a signal input and a signal output,wherein the electronic switch is turned on when the enable terminalreceives a low-level signal; a NOT gate comprising an input and anoutput, the output connected to the enable terminal and the signal inputof the electronic switch; and a fan controller comprising a generalpurpose input/output (GPIO) interface and a rotational speed controlpin, the GPIO interface comprising a second control pin connected to theinput of the NOT gate for outputting a voltage control signal, whereinthe voltage control signal is at high level at the moment of thecomputer being started up, and becomes a low-level signal via the NOTgate, the electronic switch is turned on, and transmits the low-levelsignal to the rotational speed control pin of the fan controller and thefirst control pin of the fan interface, thereby the fan is not turnedon; after a preset delay period of time after the computer is startedup, the voltage control signal at the second control pin of the GPIOinterface becomes a low-level signal under the control of the fancontroller, and the NOT gate outputs a high-level control signal to turnoff the electronic switch, the rotational speed control pin of the fancontroller outputs a pulse width modulation (PWM) signal to the firstcontrol pin of the fan interface to control the operation of the fan.